The bacterium Bacillus anthracis is highly pathogenic because of its stable spore form that resists treatment with antibiotics, its antiphagocytic capsule, and its production of potent toxins. Thus it has been studied as agent of biological warfare for some 60 years and is an extremely effective terrorist weapon. We have recently developed a novel strategy to rapidly produce fully human monoclonal antibodies after immunization and propose to use this technique to develop therapeutic antibodies against anthrax. These antibodies are derived recombinantly from expression of the immunoglobulin variable region genes of early antibodysecreting cells that arise in a massive, transient burst 7 days after immunization. This technology represents a substantial advance in monoclonal antibody production from humans and provides an opportunity to rapidly develop antibody therapies. We have now used this strategy to produce a limited number of antibodies from recipients of the anthrax vaccine. In collaboration with our U19 team we used serological studies to identify several key peptide epitopes that effectively neutralize anthrax toxin activity. The central goal of this Technology Component is to isolate the monoclonal antibodies that target these epitopes. These antibodies will be valuable as research and diagnostic reagents to assess protective immunity, and could ultimately be developed for safe passive immunization or for treatment of anthrax infection. In addition, analyses of monoclonal antibody reactivity may identify protective antibody specificities that are not dominant in the polyclonal response, or that only arise against non-peptide, structural epitopes. Although a vaccine against anthrax exists and is in limited use, primarily for vaccination of military personnel, its effectiveness is at best only good. It requires multiple and continued boosts to provide protection, and our U19 group has determined that serum from only half of those immunized can neutralize anthrax toxicity. Thus a second goal of this component is to characterize the induction of long-term B cell immunity (memory) to gain insight into why the vaccine is relatively ineffective in inducing protective immunity.